Plate steel casing joint for rotary hydraulic machines



oct. 29, 194e. J F, CORBY 2,410,201

PLATE '-'STEEL CASING JOINT FOR ROTARY HYDRULIC-MGHINESv Filed April26,1944

Il N Patented ct. 29, y:19426K This invention relates to plate steelvolute casings for rotary hydraulic machines such as hydraulic turbinesand pumps.

When volute casings are used under certain heads considerable diiicultyis frequently experienced in obtaining proper flow velocity conditionswithin the casing primarily because of the inability to have'certainportions of the plate steel casing of sufficiently small radius ofcurvature at the points where the casing joins the usual stay vane ringespecially at the small cross-sections of the casing. This difficultyhas heretofore arisen because of the necessity to provide an extendedstraight portion of the plate steel casing adjacent the stay vane ringin order toemploy usual 4riveted butt straps on each side of the 'casingjoint and thereby place the rivets in double shear.

Itis an object of my invention to provide an improved combination ofelements whereby a plate steel casing of a rotary hydraulic machine mayhave a relatively small radius ofcurvature adjacent the stay vane ringand particularly at the small cross-sections of the casing, in the caseof a volute, where the problem of making small radii of curvature isparticularly acute.

Another object is to provide an improved combination of elements forobtaining small radii of curvature, of a plate steel casing,.adjacentthe stay vane ring and still cause the rivets tobe in double shear.

Other objects'and advantages will be more apparent to those skilled inthe art from the following description of the accompanying drawing inwhich:

Fig. 1 is a partial sectional view through a casing and a portion of ahydraulic turbine;

HYDRAULIC Corby,. Philadelphia Pa., `assign otiye Works', afcrporatin GJOINT?FSI?3 Applicatiorinpm c, 194.4;y 'zel-assi (ci.44V

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Fig. 2 is anenlarged fragmentary sectional view V of the casing jointshown inFig. 1; and

Figs. 3 and 4 areV enlarged sectional views showing modied forms ofarrangements by placing the rivets in double shear.

The particular embodiments of the invention disclosed herein have beenapplied for purposes of illustration to a Francis type hydraulic turbineincluding a runner I, adjustable guide vanes 2 and stay vanes 3 whichare secured at their upper and lowerends to flow guidingportions 4 and 5extending as a'surface of revolution around the runner axis. The stayvanes and portions 4 and 5are usually cast'integrally from a stay 'vanering. A plate steel casing 6, generally of volute form, well-known inthe art, is usually riveted to the edges of the stay ringk elements 4and 5. In order to allow the casing to start its curvature 'I as closeas possible to the edge 8 of the guide vanes Ypoint 2| about No states-'i 'Y D 3 and at the same time place the rivets under double shear, Imachine a groove 9 and a small rib I0 circularly around the stay vanering preferably on the uppermost and lowermost surfaces of therespective walls and the plate metal Il of the casing is tted againstthe rib I0. A rivet strap I2 is anchored to the ring by being providedwith a circular key I3 which fits into the keyway 9.' Rivets I4 .extendthrough the stay vane ring, plate and strap I2 and are placed in doubleshear by reason of the strap I2 being keyed to and forming in elect arigid part of the stay ring structure itself. Hence, when the casing issubjected to internal water pressure so that the plate I I is placedunder tension the load will be transmitted directly to the stay ringthrough the rivets and to the plate I2 which in turn transmits the loadto key I3 and thence to the stay ring. LIn this manner it is possible toeliminate the excessive space that is normally required to produce adouble strap riveted joint which has been necessary in order to placethe rivets in double shear. Hence, with my improved arrangement, it ispossible to obtain more ideal flow conditions within the casingparticularly at the'small cross-section because of the ability to starta small radius of casing curvature close to the stay vanes.

The modification shown in Fig. 3 allows the curvature of the casing tostart very abruptly adjacent the stay vane ring plished by providing aplate metal supporting Seria surface I8 of sulicient depth on the stayring so that the plate metal casing 20 extends to a midway of the radialdepth of the guide vane I9. To provide a rm anchor for the'rivet strap22 it extends inwardly over the whole of the upper end of the stay vanering with a substantial flanged end of key 23 which overlaps the inneredge 24 of the stay vane ring. Rivets 25 secure the component elementstogether and the rivets are placed in double shear by virtue ofplate 22being anchored at 23 and 24. The lianged end 23 of the strap plate isfitted within the corner 26 of the head cover -21 well-known in the art.f

In the modification shown in Fig. 4, the casing plate 30 is placed onthe inside of the stay ring 3I while a rivet strap 32 has a key 33seated in a circular keyway of the stay vane ring. The

From the foregoing disclosure of the several` modifications, it is seenthat I have provided an I1, this being accom-V the art Without departingfrom the spirit of the I invention as set forth in the appendedc1aims.,.

I claim:

1. A rotary hydraulic apparatus comprising, in combination, a stay vanering and .a volute plate steel casing therefor having certain smallsections that are relatively small compared to others, said stay vanering having a portion overlapping one side of said plate steel casingnear its edge portion, a rivet strap overlying the other side of theVplate steel casing, and means for anchoring said strap to the stay vanering by a direct abutting contact with a transverse surface on said ringwhereby rivets extending through said strapy plate and ring will beplaced in doubleshear to provide'necessary strength and to allowcurvature of the casing at its small sections to start adjacent the stayring thereby to obtain more desirable flow conditions through the volutecasing.

2. The combination set forth in claim 1 further characterized in that ahead cover is provided with a recess to receive said stay vane ring, and

said ring has an annular ledge at its innermost edge and the strap has aflanged portion seated in saidvrecess and overlapping and engaging saidedge.

JOSEPH F. CORBY.

